1. Field of the Invention
The present invention pertains to manual control apparatus for mechanisms having movable members. Such mechanisms include actuators of the type which employ reciprocating movement of a drive member, such as a piston. The actuator may include linkage means for converting this reciprocating movement to rotational movement which is imparted to a rotating member. In particular, the invention may be used in connection with valve actuators for valves such as butterfly or ball valves having rotating valve elements such as the actuator disclosed in my prior U.S. Pat. No. 3,982,725. The manual control apparatus may also be applied to mechanisms having either strictly reciprocating or strictly rotary movement.
In such mechanisms it is highly desirable, and usually necessary, to provide manual override means for manually moving the drive member in case of failure of the electric, hydraulic, pneumatic or other system which ordinarily operates the actuator.
2. Description of the Prior Art
In my prior U.S. Pat. No. 3,982,725, the actuator includes a pair of pistons reciprocable in a cylindrical chamber. Each piston has a skirt depending longitudinally therefrom, and a rack is formed on each of these skirts. The racks engage pinion wheels carried by a shaft extending transversely through the cylindrical chamber, the shaft in turn being drivingly connected to a valve stem or other member to be rotated.
In this prior actuator, a manual override device is provided which includes wrench means for engaging and manually rotating the shaft which carries the pinion wheels.